This invention relates generally to rain rate meters, and, more particularly, to a rain rate meter which is capable of reliably delineating short-term variations in rain rate.
Many storm situations produce unexpected, localized "shafts" of severe/heavy concentrations of rain fall. Measurements taken during rain storms have shown that factors of two in rain rate variability within a matter of seconds are not uncommon. In fact, these types of measurements are consistent even in wide spread range situations, not just in severe or heavy rain scenarios. Preliminary studies indicate that areas of heavier rainfall, up to several hundreds of meters in diameter, are imbedded within storms and that these localized "shafts" of rainfall are continuously in a state of change, thus, they will form, grow while moving with the prevailing winds, and then dissipate. Consequently, their numbers, sizes and intensities are as unpredictable as their existence is predictable. For example, the effects of such heavy, localized "shafts" of severe concentrations of rainfall on the attenuation of electro-optical and communication systems and the landing or takeoff of aircraft are of particular concern.
It has long been recognized that electro-optical and communication systems are especially susceptible to attenuation because of severe/heavy rain rates. Therefore, it becomes extremely important to quickly analyze such rain rates, or the amount of rain deposited on a surface in a given amount of time. By analyzing this information, it is possible to determine the rate of such falling rain. Accordingly, steps may then be taken to lessen the attenuation effects caused by such rainfall.
In addition, studies have raised the possibility that heavy rain could be a contributing factor in a number of aircraft accidents. A sufficient amount of water striking a flying aircraft can cause a significant decrease in aerodynamic lift, increase in weight, increase in drag from the force of the raindrops striking the aircraft, and the possibility of malfunction of the aircraft engine. Since an aircraft, especially when landing or taking off, is especially vulnerable to external conditions that can alter its aerodynamic efficiency, one can easily postulate the results of such severe/heavy rainfall if a fully loaded aircraft passes through a "shaft" of severe rain at a critical point during approaching or leaving an airfield.
Heretofore, conventional tipping bucket gauges have been utilized to ascertin rain rates. Unfortunately, these types of gauges, although acceptable for rain rates from between 200 mm hr.sup.-1 to 700 mm hr.sup.-1, are ineffective at rain rates greater than 700 mm hr.sup.-1. In fact, at rain rates greater than 700 mm hr.sup.-1, water spillage encountered by conventional tipping bucket gauges begins to be a major problem, and at about 1,000 mm hr.sup.-1, the tipping bucket type rain gauge fails completely and 100% spillage occurs or the bucket merely fibrilates without tipping.
Consequently, it is clearly evident that it would be highly desirable to provide a rain rate meter which is capable of providing data over a short term and which is highly accurate in either light or heavy rainfall scenarios..